The present invention relates generally to semiconductor fabrication and, more particularly, to methods for preparing semiconductor wafers in which preparation operations are performed on a vertically oriented wafer. The preparation is configured to take place in a single enclosure apparatus.
In the fabrication of semiconductor devices, a variety of wafer preparation operations are performed. By way of example, these wafer preparation operations include cleaning operations and polishing/planarization operations, e.g., chemical mechanical planarization (CMP). One known polishing/planarization technique uses platens with planetary polishing motion. One disadvantage of this technique is that it requires multi-step procedures, which are time-consuming and relatively expensive. Another disadvantage of this technique is that it tends to produce wafers having surfaces that suffer from a relatively high degree of topographic variations.
Another known polishing/planarization technique involves circumferential polishing. In one known circumferential polishing system, a wafer is rotated in a vertical orientation by wafer drive rollers. As the wafer is rotated, a pair of cylindrical polishing pads is brought into contact with the opposing surfaces of the wafer. The polishing pads are mounted on counter-rotating mandrels disposed on opposite sides of the wafer being processed. The mandrels span across the diameter of the wafer so as to pass over the wafer center. The rotation of the mandrels causes a rotary pad motion perpendicular to the wafer diameter in a circumferential direction. During the polishing operation, nozzles direct sprays of liquid, e.g., an abrasive slurry, a chemical solution, or a rinse solution, on the opposing surfaces of the wafer.
One drawback of this known circumferential polishing system is that it provides only circumferential polishing motion. As such, the relative velocity of each pad is not uniform across each wafer surface, with the velocity near the wafer edge being greater than the velocity near the wafer center. This is problematic because it not only results in the creation of circumferential residual scratches on each of wafer surfaces, but also results in a more wafer material being removed from the center portion of the wafer than near the perimeter due to the greater dwell time experienced by the center portion of the wafer. As a consequence of this nonuniform material removal rate, each of the opposing surfaces of the wafer tends to have a flared contour, i.e., a contour in which the central portion is depressed relative to the edge portions. As the semiconductor industry moves toward the use of smaller, e.g., 0.18 xcexcm and smaller, feature sizes, such flared contours are undesirable.
In view of the foregoing, there is a need for a method and apparatus for circumferential wafer preparation that minimizes the creation of circumferential residual scratches, provides processed wafers have desired surface contours, and enables multiple wafer preparation operations to be performed on a wafer without moving the wafer between stations.
Broadly speaking, the present invention fills this need by providing apparatus or preparing wafers.
In accordance with one aspect of the present invention, an apparatus for preparing a semiconductor wafer is disclosed. The apparatus includes a frame member having first and second coaxial shaft assemblies extending therethrough. Each of the coaxial shaft assemblies including an inner transfer shaft and a hollow outer pivot shaft, each of the outer pivot shafts having a gear ring affixed thereto, and the gear rings intermeshing at an approximate midpoint between the outer pivot shafts. The apparatus further includes a first roller arm having a first end and a second end. The first end is coupled to one end of the hollow outer pivot shaft of the first coaxial shaft assembly and has one end of the inner transfer shaft of the first coaxial shaft assembly disposed therein. The second end has a first drive roller shaft disposed therein, and the first drive roller shaft is rotatably coupled to the end of the inner transfer shaft of the first coaxial shaft assembly disposed in the first end of the first roller arm. The apparatus further including a first wafer drive roller rotatably mounted on the first drive roller shaft. The first wafer drive roller is oriented to rotate a semiconductor wafer in a vertical orientation. A second roller arm has a first end and a second end. The first end is coupled to one end of the hollow outer pivot shaft of the second coaxial shaft assembly and has one end of the inner transfer shaft of the second coaxial shaft assembly disposed therein. The second end has a second drive roller shaft disposed therein, and the second drive roller shaft is rotatably coupled to the end of the inner transfer shaft of the second coaxial shaft assembly disposed in the first end of the second roller arm. A second wafer drive roller is rotatably mounted on the second drive roller shaft, and the second wafer drive roller is oriented to rotate a semiconductor wafer in a vertical orientation. A drive belt is further provided for rotating at least one of the inner transfer shafts of the first and second coaxial shaft assemblies. The apparatus also includes an actuator for controllably moving a lever arm fixed to one of the gear rings, such that movement of the lever arm causes the first and second roller arms to move from a first position to a second position.
In accordance with another aspect of the present invention, an apparatus for preparing a semiconductor wafer is disclosed. The apparatus includes a first wafer drive roller rotatably disposed on a first roller arm, and the first wafer drive roller being oriented to rotate a semiconductor wafer in a vertical orientation. The apparatus also includes a second wafer drive roller rotatably disposed on a second roller arm. The second wafer drive roller is oriented to rotate a semiconductor wafer in a vertical orientation. Each of the first and second roller arms is configured to transmit rotational power to the wafer drive roller disposed thereon, and each of the first and second roller arms is pivotable between a first position and a second position to adjust a height of the wafer drive roller disposed thereon.
In yet another aspect of the invention, an apparatus for preparing a semiconductor wafer is disclosed. The apparatus includes a wafer drive assembly having a pair of wafer drive rollers for rotating a semiconductor wafer in a vertical orientation. The wafer drive assembly is configured such that the wafer drive rollers are controllably movable from a first position to a second position. Also provided as part of the apparatus is a pair of wafer preparation assemblies movably disposed in an opposing relationship above the wafer drive assembly. Each of the wafer preparation assemblies has a first wafer preparation member and a second wafer preparation member. The wafer preparation assemblies being movable into a first position in which each of the first wafer preparation members is position to perform a first wafer preparation operation on the wafer and into a second position in which each of the second wafer preparation members is positioned to perform a second wafer preparation operation on the wafer.
It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.